Our studies are aimed at elucidating mechanisms in the immune response, using small, structurally defined antigens comprising one or two antigenic determinants. The capacity of such molecules to induce cellular and humoral immune responses in vivo and to elicit proliferative responses in lymphoid cell cultures is being assessed. Lymphoid cell populations are being fractionated to determine the cells required for responses to these antigens. It is proposed to isolate lymphoid cells with surface receptors specific for defined determinants, using affinity chromatography. The ultimate goal of the project will be the isolation and comparison of antigen receptor molecules from B and T lymphocytes.